Neurohipófise

A neurohipófise ou pituitaria posterior comprende o lóbulo posterior da hipófise ou pituitaria do encéfalo e forma parte do sistema endócrino. Malia o seu nome, a neurohipófise non é unha verdadeira glándula per se; senón máis ben está formada en grande parte por un conxunto de proxeccións axónicas procedentes do hipotálamo que terminan alí.

Esquema da hipófise ou pituitaria, coa pituitaria posterior ou neurohipófise en azul (só se mostra a eminencia media).

Corte saxital medio dunha hipófise de mono.

 Precursor    = Tubo neural (crecemento inferior do diencéfalo) |

Anatomía

The posterior pituitary consists mainly of neuronal projections (axons) extending from the supraoptic and paraventricular nuclei of the hypothalamus. These axons release peptide hormones into the capillaries of the hypophyseal circulation. In addition to axons, the posterior pituitary also contains pituicytes, specialized glial cells resembling astrocytes.

Classification of the posterior pituitary varies, but most sources include the three regions below:

Pars nervosa

Also called the neural lobe or posterior lobe, this region constitutes the majority of the posterior pituitary and is the storage site of oxytocin and vasopressin. Sometimes (incorrectly) considered synonymous with the posterior pituitary, the pars nervosa includes Herring bodies and pituicytes.

Infundibular stalk

Also known as the infundibulum or pituitary stalk, the infundibular stalk bridges the hypothalamic and hypophyseal systems.

Median eminence

This is only occasionally included as part of the posterior pituitary. Other sources specifically exclude it from the pituitary.

A few sources include the pars intermedia as part of the posterior lobe, but this is a minority view. It is based upon the gross anatomical separation of the posterior and anterior pituitary along the cystic remnants of Rathke's pouch, causing the pars intermedia to remain attached to the neurohypophysis.

Hormonas segregadas

Hormones known classically as posterior pituitary hormones are synthesized by the hypothalamus. They are then stored and secreted by the posterior pituitary into the bloodstream.

Hormone	Other names	Symbol(s)	Target	Effect	Source
Oxytocin	Pitocin (trade name)	OT	Uterus, mammary glands	Uterine contractions; lactation	supraoptic and paraventricular nuclei
Vasopressin (antidiuretic hormone)	Arginine vasopressin, argipressin, antidiuretic hormone	VP, AVP, ADH	Kidneys or Arterioles	Stimulates water retention; raises blood pressure by contracting arterioles, induces male aggression	supraoptic and paraventricular nuclei

Enfermidades

Insufficient secretion of vasopressin underlies diabetes insipidus, a condition in which the body loses the capacity to concentrate urine. Affected individuals excrete as much as 20 liters of dilute urine per day. Oversecretion of vasopressin causes the syndrome of inappropriate antidiuretic hormone (SIADH).

Galería de imaxes

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  A neurohipófise comprende o lóbulo posterior da glándula hipofisaria.
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  Núcleos hipotalámicos

Véxase tamén

Adenohipófise Hipófise